#include	<stdlib.h>
#include	<stdio.h>

FILE	*s_in, *a_in, *s_out;

int
pass()		/* copy byte from s_in to s_out and return it */
{
	int	c;

	if ((c = getc(s_in)) == EOF)
		exit(0);
	putc(c, s_out);
	return c;
}

void
passn(int n)	/* copy n bytes from s_in to s_out */
{
	int	i;

	for (i = 0; i < n; i++)
		pass();
}

void
copyn(int n)	/* copy n bytes from a_in to s_out, skip n bytes of s_in */
{
	int	i;

	for (i = 0; i < n; i++) {
		getc(s_in);
		putc(getc(a_in), s_out);
	}
}

void
stream(int s)	/* process stream of type s */
{
	int	c, l, n;

	for (;;) {
		while (pass() != 0)			/* sync */
			;
		n = 1;
		while ((c = pass()) == 0)		/* padding */
			n++;
		if (n < 2 || c != 0x01 || pass() != s)	/* start code */
			continue;
		l = pass();
		l = (l << 8) | pass();			/* packet length */
		n = 1;
		while ((c = pass()) == 0xFF)		/* stuffing */
			n++;
		if ((c >> 6) == 1) {			/* buffer size */
			n += 2;
			pass();
			c = pass();
		}
		switch (c >> 4) {			/* time stamps */
		case 2:
			passn(4);
			n += 4;
			break;
		case 3:
			passn(9);
			n += 9;
		}
		copyn(l - n);				/* data */
	}
}

FILE	*
fileopen(char *f, char *m)
{
	FILE	*o;

	if ((o = fopen(f, m)) == NULL) {
		perror(f);
		exit(1);
	}
	return o;
}

int
main(int argc, char *argv[])		/* audiodub - Copyright (C) 1997, Bruce Ellis */
{
	if (argc != 4) {
		fprintf(stderr, "usage: %s mpegin audioin mpegout\n", argv[0]);
		return 1;
	}
	s_in = fileopen(argv[1], "rb");
	a_in = fileopen(argv[2], "rb");
	s_out = fileopen(argv[3], "wb");
	stream(0xC0);
	return 0;
}